1. Field of the Invention
The present invention pertains to chlor-alkali cells. More particularly, the present invention concerns cathodes for use in cholor-alkali cells. Even more particularly, the present invention concerns metal coated cathodes for chlor-alkali cells.
2. Prior Art
The electrolytic decomposition of solutions of alkali metal chlorides for the production of chlorine, caustic and hydrogen has long been known. Generally speaking, chlorine gas is generated at the anode; hydrogen gas at the cathode and OH ions (caustic) in the electrolyte. Conventionally, a diaphragm, which is usually secured to the cathode, segregates the anode area from the cathode area. This construction is employed in both conventional monopolar cell arrangments as well as in bipolar filter press cell arrangements.
Typcially, in operating the cells, a voltage of three to four volts is applied thereacross. Although, theoretically, a lower voltage is required to decompose the alkali metal chloride, the higher voltage is utilized because of the resistance of the alkali metal chloride solution and mainly because of the "overvoltage" at the electrodes. This overvoltage results in greater power consumption with the attendant increase in costs of production.
While the prior art has devoted considerable effort in developing improved anodes, the same effort has not been devoted to improving the cathodes. With respect to the cathodes, it has been known that the hydrogen overvoltage at the cathode is a function of the type and surface condition of the cathode material. Therefore, attempts have been made to reduce the hydrogen overvoltage. In U.S. Pat. No. 3,282,808 there is taught the impregnation of a ferrous metal cathode with particles of nickel. However, by embedding the metal into the cathode, hydrogen bubble release is greatly reduced, thereby inhibiting the efficacy thereof.